1. Field of the Invention
This invention relates to a method for airborne gravity and magnetic field surveying with which greater accuracy of data collection and processing is obtained than has heretofore been available.
2. Brief Description of the Prior Art
It has been proposed to use airborne vehicles for gravity surveying as pointed out in Reviews of Geophysis, Vol. 5, No. 4, November, 1967, pages 447 to 526, published by The American Geophysical Union of 2000 Florida Avenue, N.W., Washington, DC 20009 commencing at page 520 to 524 for fixed wing airborne vehicles.
A review of airborne gravity surveying activities with respect to helicopters can be found in "Airborne Gravity Surveying, Technical Information", published March, 1981, by Carson Geoscience, Perkasie, Pa. This publication was authored by Franklin D. Carson and William R. Gummert, the inventors herein and describes prior attempts for surveying and the inventors efforts.
Various patents have been issued which set forth apparatus for gravity surveying.
Boitnott in U.S. Pat. Nos. 3,011,347 and 3,308,338; Gustafsson U.S. Pat. No. 3,180,151; and Brede U.S. Pat. No. 3,447,293; and Hutchins Canadian Patent No. 652,757 disclose instruments for measuring gravity or derivatives of gravity of the earth's gravity field, but do not disclose practical systems for accurate airborne surveying.
LaCoste U.S. Pat. Nos. 2,293,437; 2,377,889; 2,964,948; 2,977,799; 3,474,672; Heiland U.S. Pat. No. 2,626,525; Worden U.S. Pat. Nos. 2,674,887 and 3,211,003; Graf U.S. Pat. No. 3,019,655; Ememrich U.S. Pat. No. 3,033,037; Slater U.S. Pat. No. 3,062,051; Hodge et al U.S. Pat. No. 3,194,075; Ward, U.S. Pat. No. 3,495,460; Kuzivanov et al U.S. Pat. No. 3,501,958; Wing U.S. Pat. Nos. 3,546,943 and 3,583,225, show navigation and/or gravity meters but do not show practical systems for accurate airborne surveying.
Klasse et al. U.S. Pat. No. 2,610,226; Jensen U.S. Pat. No. 2,611,802; Rumbaugh et al. U.S. Pat. No. 2,611,803; and Pittman U.S. Pat. No. 4,197,737 show method and/or apparatus for conducting surveys for geophysical or magnetic explorations but do not discuss or treat airborne gravity surveying.
O'Neill U.S. Pat. No. 4,359,733 describes a satellite system which provides signals whereby the position of an aircraft can be established. However, there is no suggestion in O'Neill of controlling the aircraft's flight by means of the satellite signals.
Airborne surveying, and particularly airborne gravity measurement requires a very high degree of accuracy as small variations in data are highly significant to indicate the presence or absence of oil and gas deposits.
The Carson Geoscience article which was authored by Franklin Carson and William Gummert the inventors herein describes the prior art equipment and method of airborne surveying used by others.
As described in the article PP 2-16-2-18 Entech was a company owned by the co-inventor William Gummert and preliminary work was done by him to investigate the feasability of using airborne gravity surveying to develop data which could be used to construct a map of the geological characteristics of an area of survey. While the Gummert-Entech experiments of 1970-1971 disclosed that airborne gravity surveying was feasible, it was not possible to achieve the stability of the aircraft required to produce accurate data. In addition the aircraft could not be flown on preplotted lines because the necessary equipment was not available. Accordingly, the data collected was not of sufficient accuracy to provide an accurate map. The article on Page 2-18-2-20 describes the early Carson attempts to demonstrate the feasibility of airborne surveying in comparison with a land based system, which produced values known to be accurate and with which the airborne data could be compared. While data was obtained that could be used to map an area of survey, the apparatus and equipment were further refined and developed to its present state where it is now possible to obtain data that is accurate enough to be commercially successful.
The proposals heretofore made for airborne surveying do not provide adequate stabilization of the aircraft with respect to speed, do not provide for level flight, do not provide accurate navigation and steering, and do not with other requirements for accurate surveying, measure the gravity or magnetic field, and have other shortcomings.